The invention concerns an implantable electrode arrangement which includes an electrode lead with a plurality of electrically conducting surface regions in the region of the distal end for outputting electrical signals to a heart and/or for receiving signals from a heart. The output and/or received signals can be electrically connected by way of the electrode lead to a cardioelectric device for a defibrillator or cardiac pacemaker where the cardioelectric device receives electrical signals and/or outputs pulses.
Electrode arrangements with an electrode line and a plurality of electrically conducting surface regions, for example of tip or ring electrodes, at a distal end of the electrode line are known for example from EP 0 571 797, U.S. Pat. No. 4,848,352 and U.S. Pat. No 4,628,934. In known electrode arrangements, the electrically conducting surface portions which serve as stimulation or sensing electrodes are individually connected to a cardiac pacemaker or defibrillator by means of electric lines which extend in the electrode lead. Each of the above-mentioned publications also describes selecting from the plurality of electrodes or electrode combinations, the respectively most suitable ones thereof in order to use them for example for stimulation of a human heart. A disadvantage with the known electrode arrangements is that they can usually only be employed together with specifically adapted cardiac pacemakers or defibrillators which make it possible at the proximal end of the electrode lead or line to contact all feed lines which lead to the electrically conducting surface regions.
Conventional electrode arrangements are those in which only one or two electrical conductors extend in the electrode line, depending on whether the electrode arrangement is intended for unipolar or bipolar stimulation.
Electrode lines with a single-wire connection between the proximal end of the electrode line and the electrically conducting surface regions at the distal end of the electrode line are suitable for unipolar stimulation in which stimulation pulses are outputted between the electrically conducting surface regions at the distal end of the electrode line and a neutral electrode such as for example a casing of a cardiac pacemaker. Also known moreover is bipolar stimulation in which the stimulation energy is outputted between various ones of the electrically conducting surface regions at the distal end of the electrode line. For bipolar stimulation, the electrode line has a two-wire connection between the proximal and distal ends, such connection being made by way of two separate electric lines.
The object of the invention is to also make available the advantages of electrode arrangements having a plurality of electrically conducting and individually operable surface regions, for cardiac pacemakers or defibrillators having conventional one-wire or two-wire connections.
According to the invention, that object is attained by an electrode arrangement of the kind set forth in the opening part of this specification, which is distinguished by switching means that are of such an arrangement and configuration that the connection between individual ones of the electrically conducting surface regions and the cardioelectric devices can be permanently switched on or off in the region of the electrode lead. Such an electrode arrangement makes it possible for firstly any of the electrically conducting surface regions to be selected by virtue of receiving or outputting electrical signals and then used permanently by way of a conventional one-wire or two-wire line in the electrode lead with the cardioelectric device such as a defibrillator or cardiac pacemaker.
For that purpose it is advantageous if the switching means are of such a configuration that they retain their switching state in the current-less condition.
In a preferred embodiment, the switching means are electrically actuable by way of the electrode lead. For that purpose, the electrode lead preferably has a decoder which is connected on the one hand to the switching means and on the other hand to at least one electric linexe2x80x94for example the usual one-wire or two-wire line which connects the electrically conducting surface regions to the cardiac pacemaker. The decoder is of such a nature that it can receive control signals by way of the electric line and can individually actuate the switching means in dependence on the control signals. In the minimum situation, an electrode arrangement of that kind needs only one single electrical conductor which goes from the proximal end of the electrode lead to the switching means, the decoder and the electrically conducting surface regions at the distal end of the electrode lead. The reference potential for the control signals can then be afforded, for example, by way of a neutral electrode with the casing of the pacemaker. After the most suitable electrodes or electrode combinations have been ascertained, then by means of the decoder and the switching means they can be permanently connected to, for example, a cardiac pacemaker by way of the one electric line in the electrode lead. The cardiac pacemaker can be a conventional cardiac pacemaker which then also enjoys the advantages of the individually ascertained, most suitable electrode configurations.
For the permanent connection of the electrically conducting surface regions to the electrical conductor in the electrode lead or conversely for permanently separating individual surface regions from the electrical conductor, it is possible to use electric components which for switching or breaking the connection require a higher level of electrical power than can be made available for example by way of the one-wire conductor and the neutral electrode as the counterpart electrode. In order to be able to use such electric components, the electrode arrangement includes preferably an energy storage means which is connected to the switching means and/or the decoder and which can be charged up by way of the electrode lead with a lower level of power than it can output by way of the switching means and/or the decoder. Preferably, the energy storage means is an electrical capacitor which is charged with a high level of resistance, for example, by way of a fine-wire line and the neutral electrode and can quickly output the electrical energy accumulated in that way for switching the switching means. This can be achieved, for example, by switching through a power field transistor or burning through a thyristor. In that way a switching connection is permanently made or permanently broken. The last-mentioned case is the preferred one, in which the switching elements are such that, for switching off a connection between the electrode lead and an electrically conducting surface region, the connection can be permanently destroyed. The energy storage means is preferably adapted to output the energy required for that purpose.
Even if the electrical energy storage means, in particular in relation to such electrodes with a single-wire connection between the proximal and the distal ends, because of the level of power which is to be kept down for charging the capacitor, enjoys particular advantages so that affected heart tissue is not already stimulated upon charging of the energy storage means, such an energy storage means can equally advantageously be used in relation to an electrode lead with a two-wire connection between the proximal and the distal ends, with which, due to the principle involved, higher levels of power can be transmitted to the energy storage means, than in the case of an electrode lead with only a one-wire connection.
Particularly for checking out individual surface regions or combinations, a preferred electrode arrangement is one which includes control means which at the input side can be connected to the cardioelectric device by way of at least one electric line for signals to or from the electrically conducting surface regions and which at the output side are connected to the electrically conducting surface regions which are such that they are controllable by control signals received by way of the electric line, in such a way that individual surface regions or combinations of surface regions can be connected to the cardioelectric device for outputting and receiving signals for ascertaining the permanent connection to the electrically conducting surface regions which are suitable for the cardioelectric device. The last-mentioned variant therefore does not concern permanent connection of the electrically conducting surface regions to the cardioelectric device, but a testing connection of the surface regions to the device prior to permanent setting of a suitable electrode combination.
An alternatively preferred electrode arrangement is distinguished by a rod or bar which is guided longitudinally movably or rotatably relative to the electrode line and which has actuating elements for mechanical switching elements, with which the connection between individual ones of the electrically conducting surface regions and the cardioelectric device can be permanently switched on or off in the region of the electrode lead. By means of such a bar and the switching elements, the switching elements can be so displaced or rotated in the electrode lead that they selectively make or break a contact between individual ones of or a plurality of the electrically conducting surface regions and an electric line in the electrode lead. As the corresponding mechanical switching elements do not change over without being actuated by the bar, in that way a connection is permanently made or interrupted between the electrically conducting surface regions and the electric conductor in the electrode lead.
In connection with the last-mentioned alternative embodiment, a preferred electrode arrangement is one in which the switching elements are arranged longitudinally movably or rotatably in the region of the distal end of the electrode lead and are in electrical contact with at least one electric line in the electrode lead, and also have contact regions which, in one of at least two possible positions of the switching elements, contact a counterpart contact which is connected to at least one electrically conducting surface region, and further have switching cams or projections with which a switching element is movable by means of corresponding counterpart cams or projections on the bar, by means of the bar, in such a way that the switching means are movable by means of the bar into a respective position of connecting a surface region to the cardioelectric device and a position of separating a surface region from the cardioelectric device. The principle of two cams or projections which are to be brought into engagement with each other in order to rotate and longitudinally slide a mechanical element is known to the man skilled in the art in all its various forms and can be easily transferred to a bar with a plurality of actuating cams or projections in which the actuating cams or projections are so displaced relative to each other that all mechanical switching elements can be displaced or rotated by a bar individually and independently of each other.
In accordance with the invention the above-specified object is also achieved by means of a method of operating the described electrode arrangement, in which firstly surface regions which are suitable for signal reception and/or stimulation are ascertained and then the appropriate surface regions are permanently connected to at least one electric line of the electrode line while the other surface regions are permanently separated from the electric line. The method is therefore a two-stage method, firstly provisional connections are made between the electrically conducting surface regions and for example a cardiac pacemaker in order to test the electrically conducting surface regions or combinations in terms of their suitability. The above-mentioned control means serve for that purpose. Then, the most suitable surface regions are permanently connected to an electric line leading to the proximal end of the electrode line or accordingly all surface regions apart from the most suitable surface regions are permanently separated from the electric line.